Dr. Zakon proposes to use the communication signal of a weakly electric fish as a model system to elucidate how ion currents are regulated and the significance of this regulation for behavior. The electric organ discharge (EOD) is sexually-dimorphic, hormone-sensitive, and individually-distinct; the waveshape of the EOD is intimately dependent on and reflective of the membrane properties of cells in the output motor system. The investigators wish to understand how the magnitudes and kinetics of the ion currents in the emitter--the electrocytes--shape the signal, and how they are regulated. In particular, they wish to characterize the delayed rectifying K+ current further, understand what processes give rise to the systematic variation in its kinetics, and how these may be regulated by sex steroids. They will test whether variation in current kinetics is influenced by phosphorylation and/or transcriptional control of the channel (i.e. different channel genes, splicing or editing within a single channel gene, or the expression of a beta subunit). In addition they will study how the magnitude of both the K+ and Na+ currents are co-regulated by second messengers and how this results in changes in the amplitude of the signal around the fish; these changes in signal amplitude likely influence the distance over which these signals are received in the fish's environment. Understanding how ion channels function and are regulated is critical to our fundamental knowledge of excitable cells, especially as malfunctions of ion channels are increasingly recognized in a variety of diseases.